This invention relates to a fuel supply system for the pressurized carburetor of an internal combustion engine, and more particularly to an improved fuel feed system for an engine.
As is well known, charge forming devices such as carburetors employ a float controlled fuel bowl that is intended to provide a uniform fuel head for the discharge circuits of the charge forming device. The float operated valve of such devices is intended to maintain a uniform fuel level so as to minimize variations in mixture strength. Although this is the principle of operation of such devices, in practice the float operated valve does not truly maintain a uniform fuel head under all running conditions.
The problems noted in the preceding paragraph are particularly prevalent in engines having forced induction systems, such as those employing superchargers, be they direct driven or turbochargers. Throughout this specification and in the claims the word "supercharger" shall be used generically to cover both types of devices. When a supercharger is employed, and particularly one in which the blower output is delivered to the inlet of the charge forming device of the carburetor, it has been the practice to insure that the resulting pressure is also transmitted to the fuel bowl so that a more uniform fuel discharge relationship will be established. If the fuel bowl is not so pressurized, the discharge of the fuel circuit would be into an area of higher pressure as the blower pressure increased. This would result in a reduced fuel flow from that desired. Although the pressurization of the fuel bowl will minimize the variations in fuel flow due to differences in pressure between the discharge of the fuel circuit and the air pressure in the fuel bowl, another problem results from such an arrangement. That is, the fuel pump which delivers fuel to the fuel bowl must act against a higher pressure at high engine speeds and with high boost pressure. This will cause diminished fuel flow, variations in the fuel level in the fuel bowl and resulting fuel discharge variations and uneven running.
It is therefore a principal object of this invention to provide a improved fuel feed system for an internal combustion engine.
It is another object of this invention to provide a fuel feed system for an engine that minimizes variations in fuel flow due to pressure variations in the charge forming device and induction system.
It is a further object of this invention to provide an improved fuel feed system for a pressurized carburetor wherein the fuel pump discharges into the fuel bowl at substantially consistant pressure differiential regardless of the pressure in the fuel bowl.
Still another problem exists in conjunction with the fuel feed system of an internal combustion engine. Frequently when the engine is shut off, the fuel has a tendency to be forced back out of the fuel bowl into the fuel tank or into a overflow condition. This results from the heating of the fuel bowl and the generation of an increased pressure which tends to cause the fuel to back flow. In addition, this condition can tend to cause difficulty in restarting a hot engine due to a condition commonly known as "vapor lock."
It is, therefore, a further object of this invention to provide a fuel feed arrangement for an internal combustion engine which reduces the loss of fuel from the fuel bowl when the engine is stopped.
It is another object of this invention to provide a system wherein a vapor lock condition may be readily cured.